FRANKLIN -- Back when the Earth was young -- say, 1.3 billion years ago -- much of this area of the globe was covered by a shallow sea. The seabed was the original mantle, long before the continents started to drift around.

The bottom was layer-on-layer of pure white mineral, which had precipitated out of the seawater and gathered on the sea floor.

Verbeek, a retired geologist with the U.S. Geological Survey, is described by friends as "the world's foremost authority" on Franklin minerals, especially those that seem to glow in the dark under ultraviolet light (more on that later).

Verbeek was in his workshop tucked in a back room of the Franklin Mineral Museum and was describing how this tiny spot on a map of the world is famous across the world for its minerals that glow in the dark under UV light.

While the mines in Franklin closed down on Sept. 30, 1964, rockhounds and prospectors have gone over, around and through any pile of rocks they could find in the borough.

Most known sites have been picked over, but on Saturday, in a long-vacant lot off High Street, members of the Franklin Ogdensburg Mineralogical Society got a chance to prospect an area on the edge of the underground formation that miners cut into for more than a century, extracting untold wealth and beautiful natural art.

Back to the pre-, pre-, prehistoric recounting: The chemical composition of that seabed changed subtly as the eons passed. Forces under the sea also changed as the huge tectonic plates that make up the Earth's outer crust moved and heaved, running head-first into each other in the slowest of collisions, or ran over or under the other plate.

With pressure and time, that solid white seabed became what is now called Franklin marble, a layer of rock that stretches from the Limecrest area of Sparta to north of Franklin.

Along with that white seabed, scientists now believe, other elements such as zinc, iron and manganese came along and were embedded.

While nature was working on that area, in a much smaller area another mix of processes, temperatures and ingredients was at work.

Cracks were created, crevices were conceived, and hot, molten rock, super-heated gases and water, in all its forms, worked their magic on that layer of seabed.

In a kitchen, a mix of ingredients, processes and temperatures is the difference between fried chicken and chocolate chip cookies.

In the Earth under what is now High Street and bounded by Main Street and Buckwheat Road, the mix of ingredients and temperature did something unique.

For along with the metal elements, the special conditions were also forming minerals, lying side-to-side with the zinc and iron and manganese, necessary for a growing America.

The metal elements were discovered in Franklin as they were in much of Sussex County in the early history of the country. Many small mines operated along the walls of the Wallkill River. In the early 1900s, those mining efforts were consolidated under the umbrella of the New Jersey Zinc Co.

For many years, that company mined the most zinc of any mine in the United States.

Also mixed in the zinc-carrying ore that the miners worked to extract were other rocks -- sparkling rocks, crystalline rocks, rocks with streaks and flecks of minerals.

The names roll off the tongue of some borough natives, who can tell at a glance the more common ores and "ites" found in the borough.

In all, 375 unique minerals have been found among those rocks. The miners often took them home, whiling away their time above ground with making pieces of art. Sometimes it was the colored sand collected from the tailings (leftover dust from the ore crushing process), carefully sifted to make colorful pictures.

Those miners were well-acquainted with the Franklin minerals and some of their abilities to give off bright colors when under an ultraviolet light.

One of the first people to observe fluorescence in minerals was George Gabriel Stokes in 1852. He noted the ability of fluorite to produce a blue glow when illuminated with invisible light "beyond the violet end of the spectrum." He called this phenomenon "fluorescence" after the mineral fluorite.

And yes, fluorite has been found in Franklin.

The property where members of the Franklin Ogdensburg Mineralogical Society (who call themselves "FOMS") were prospecting on Saturday is site of a long-forgotten mine shaft and is privately owned.

"I was making a presentation to FOMS in May, and during the conversation the High Street site came up," said Franklin native Phil Crabb, a Sussex County freeholder and co-owner of the site.

There, poking up out of the ground, is the westernmost point of the Franklin orebody. An orebody is the underground formation that has the highest yields of the sought-after ore. For precious metal, it's often called the "motherlode."

Crabb noted the area has been fenced off since the 1940s and he and his partner John Snowden, rock and mineral collectors since their youth, had used a small backhoe to turn over boulders and open up the area for easier exploration.

Also coinciding with Saturday's event was a previously planned documentary crew that was to be in the area filming a club event.

"It's pretty exciting," Crabb said, "Here's the chance for someone to find something that was created 1.2, 1.3 billion years ago."

Bruce A. Scruton can also be contacted on Twitter: @brucescrutonNJH or by phone: 973-383-1224.

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